1. Field of the Invention
This invention relates to manipulating workpieces incident to transporting of the workpiece by a conveyor for the application of decoration in a decorating facility. More particularly, the present invention relates to providing a manipulating apparatus to grip a workpiece at a preselected distance along the length of the workpiece so as to present an end of the workpiece to a support such as a conveyor or a vacuum chuck with precise placement of the workpiece during disengagement phase of the manipulation operation.
2. Description of the Prior Art
As shown in U.S. Pat. Nos. 2,231,535; 2,261,255; 2,721,516; and 3,146,705 intermittent motion type decorating machines are known in the art and provide a drive system to impart intermittent traveling motion to the workpieces such as containers made of glass or plastic. A container is moved through a predetermined distance, stopped, moved again through a predetermined distance, stopped and again moved until each container through the sequence of motions moves completely through the decorating stations of the machine. A decorating station will be provided at each place where the container comes to a stop. At the decorating station, a decorating screen is displaced into line contact with the surface of the container by as associate squeegee and then the container is rotated and the squeegee remains stationary for a decorating process. It is advantageous for this decorating process to provide that the container surface which is to receive the decoration is horizontally oriented. This is because the printing medium is subject to the influence of gravity whereby the printing medium can be uniformly spread across the screen surface when the squeegee spreads the printing medium horizontally. When the ink spreading surface of the squeegee is oriented vertically, it is difficult to maintain an adequate supply of ink throughout the height of the printing screen. The advantages of decorating the workpiece while the workpiece is orientated horizontally is equally applicable to other examples of workpieces such as glass tumblers where, for example, it is possible to grip the workpiece at one end only. With respect to a soda bottle, for example, the bottle mouth site usually regarded as too small of an area to sustain the weight of the bottle by a vacuum chuck. Alternative support systems can be used such as engaging only the bottom base or alternate the opposite ends of the soda bottle.
There are, however, machines known in the art for applying decoration to a surface while orientated vertically. An example of such a machine is disclosed in U.S. Pat. No. 4,463,371. The present invention seeks to provide a workpiece manipulating device useful to supply workpieces to a discharge conveyor and/or from a supply conveyor at spaced apart time intervals in a reliable fashion and in an operative relation with a support structure used to move a workpiece in a decorating machine. In this regard, it is necessary to provide a manipulative structure suitable to supply or receive a succession of workpieces from a support structure such as vacuum chuck which is part of the printing machinery used to present the workpieces in succession to printing stations from supply and delivering conveyance structures having fixed a plane of workpiece support. It is inadequate to require changes to the elevation of the conveyor belt used to support the workpiece because, among other things, the destruction to the synchronous relation between the operation of the manipulator apparatus and the conveyor and the receiving site for the workpiece by a vacuum chuck of the printing machine. The removal of a workpiece from the supply conveyor or the placement of a workpiece on a delivery conveyor requires a manipulative operation dependent upon the height of the workpiece on the conveyor as well as the transverse dimensions along the height of the workpiece. A glass tumbler and more dramatically, a glass stemware have width dimension properties that are dramatically different, not only transverse but also must be orientated during the manipulation procedure so that gripper arms can pass freely into and out of supporting contact. It is a typical and most desirable to transport a tumbler while vertically orientated to minimize space requirements but orientated horizontal for the decorating process.
Certain workpieces because of their configuration and material of construction, such as glass tumblers which are tall truncated cones with a flat bottom, must be moved with great precision from a carrier in a decorating machine to a delivery conveyor. Ever changing variables from glass tumbler to a glass tumbler include surface irregularities at the touch sites where the glass tumbler will be supported by the gripping members used to unload the workpiece. Also the glass tumbler should move along a path of travel that avoids the possibility of impact with the conveyor structure used to discharge the tumbler to the decorating machine. Impact must also be avoided with the tumbler while a retention device used to hold the tumbler mover to the discharge site from the decorating process. The avoidance of impact is particularly acute to satisfy necessary operation speeds for an acceptable through-put capacity of the decorating machine. Operator fatigue precludes the use of workers to unload workpieces, such as glass tumblers, from a decorating machine. Moreover, in a decorating machine using silk-screen printing techniques, after the screens are provided with an ink supply, the printing operations should proceed without extended periods of interruption. Printing delays due to down time of allied equipment allow an unwanted dispersement of printing medium through the silk-screen without extraction of the printing medium from screen by a workpiece. The matter is particularly acute when, for example, multiple colors are printed using multiple printing stations. When four different colors are being printed in a single decorating machine, each of the four different printing stations for the various colors must be subject to a clean-up operation before the decorating machine can be placed back on a production basis. Restarting the printing operation after a delay requires cleaning smeared printing from workpieces which is very labor intensive.
In our co-pending patent application Ser. No. 07/771,638, Filed Oct. 4, 1991, there is disclosed an apparatus to load workpieces on a carrier for a decorator. The apparatus includes a conveyor to deliver a workpiece to a transfer site, a gripper including a displaceable gripper movable relative to a stationary gripper for supporting a workpiece at the discharge site, a swing arm supporting the gripper at one end thereof for movement between the workpiece transfer site and a workpiece loading position, an actuating lever movable with the swing arm for moving the displaceable gripper into a workpiece release position with the stationary gripper at the workpiece loading position, a drive coupled to the end of the swing arm opposite the gripper for reciprocating the swing arm between a workpiece receiving position and a workpiece discharge position, and cam drive to synchronize the operation of the drive for reciprocating the swing arm and the actuating lever for moving the displaceable gripper.
In such a loading system workpieces can be presented to a support structure of a decorating machine through the operation of the grippers and operation of the drive mechanism necessary to translate the gripper from the workpiece receiving position and a workpiece discharge position. In this loading mechanism the workpieces are always received at a designated workpiece receiving site that is fixed in relation to all other structure of the decorating machine so that there is no need to undergo costly and time consuming setup operations to accommodate changes from one dimensional characteristic workpiece to a different dimensional characteristic workpiece. When converting, for example, from one glass tumbler size to a different glass tumbler size, the gripper arms are adjusted to bring them into suitable gripping relation with the workpiece but there is no need to reposition the conveyor with respect to the support structure of the decorating machine for the workpiece to accommodate the change to the size of the workpiece. This is because the workpiece is engaged at a predetermined distance from the support surface of the conveyor and this predetermined distance remains uniform throughout the transporting operation to lift and transport the workpiece from the conveyor to the support structure for the decorating machine. The support structure in turn always receives the workpiece while the gripper arm is engaged with the workpiece at a never changing relation from the edge or rim of the workpiece by which it will be supported by the support structure for the decorating machine.
The present invention provides a manipulator structure that will solve the problem of loading and/or unloading workpiece in a decorating machine wherein there exists selective positioning of a gripping structure as an operative unit to accommodate workpieces of a variety of shapes and varying dimensions as an incident to the decorating process and in conjunction with a conveyor operative at a fixed, predetermined elevation. The loading operation and the unloading operation require suitable structure to accommodate the widely varying height dimensions of a given line of products to be processed on the decorating machine. While the manipulating apparatus for the loading operation may receive a workpiece while supported on the rim structure of the workpiece preference or other considerations may dictate that the workpiece be supported on its conventional bottom. Thus, there will no longer exist a fixed and predetermined dimensional relation between the gripper at the rim of the workpiece by which is will be presented for support to a vacuum chuck by the manipulated structure. A similar relation also exists on the unloading phase of the decorating process wherein the dimensional relation between the workpiece as presented to an unloading structure changes with the height of the workpiece so that it is necessary to accommodate the varying height when depositing the workpiece on a conveyor. The dimensioned relationship between the gripper at the support site and the base of the workpiece changes from the size of the workpiece and so does the dimensional relationship between the gripping site and the surface of the workpiece by which it will be supported during conveyance during unloading.